To obtain an optically efficient joint between ends of two facing optical fiber strands used for communication and/or light transmission has proved a difficult task. The difficulty is that the ends of each of the fibers must be face-to-face and share a common axis or else there will be attenuation losses.
This is because any rays emitted from the end of the optical core of one fiber if not accepted by the opposing end of the receiving fiber will result in a loss of the received signal. Efficiency in this instance is reduced in power in the ratio of: ##EQU1##
This efficiency is usually indicated as a logarithmic function designated in decibels and having the formula: EQU N=10 log.sub.10 P.sub.1 /P.sub.2
wherein:
N=the power loss in decibels PA1 P.sub.2 =energy received by 2nd fiber PA1 P.sub.1 =energy emitted by 1st fiber
By using this notation, the total of all the losses in a system (in decibels) is the arithmetic sum of the losses of each part.
Optical fibers are prepared for mechanical alignment by fracture to produce a planar face normal to the fiber axis of the fibers or the ends of the fibers are ground and polished to produce an optical surface normal to the fiber axis.
It is one thing to prepare an optical fiber and another problem to insure alignment along the axis of the two fibers. Any eccentricity with respect to the common axis will result in an attenuation loss or loss in efficiency at the joint.
In general, when two optical fibers are to be brought in face-to-face relationship with each other, the approach has been the fabrication of elements of the connector to extremely close tolerances and to insure that the fine bores for receiving the optical fibers will be in proper alignment.
This ignores, however, the fact that the bores for receiving the optical fibers are oversized with respect to the fibers to enable the receipt of the optical fibers in slidable relationship and to provide for the addition of a cement to bond the fiber in place.
Unless by chance each fiber is perfectly centered in their receiving bores, the axis of the abutting fibers will not be in line and a loss of efficiency will result. The probability of making a coupling with both optical fibers sharing a common axis at the point of coupling is very small. With many connectors over a long span, the sum of the attenuation loss will result in an unacceptable loss in overall efficiency.
The present invention is to provide a method for insuring perfect alignment between the axis of two facing optical fibers in a coupling or other connection when the facing fibers are bonded in a bore by cement and apparatus to achieve this result, even in the field.